A pulsation damping device for a pump of this type, has been disclosed in, for example, Japanese Patent Publication Laying-open Nos. 6-17752 and 8-159016.
The pulsation damping device for a pump shown in Japanese Patent Publication Laying-open No. 6-17752 is illustrated in FIG. 4. The proposed pulsation damping device has a hermetical device body casing 60, a liquid chamber 61a disposed inside the device body casing 60, for functioning as a storage of the liquid, which sucks and stores temporarily the transported liquid by the reciprocal pump, and discharges it, and a gas chamber 61b disposed inside the device body casing 60, which is separated from the liquid chamber 61a via an extendable and contractible diaphragm 62 for suppressing pulsation, so as to seal a gas, whereby the pulsation suppression diaphragm is extendably and contractibly deformed by pulsation of the discharge pressure of the pump. The proposed device has the above configuration, thereby making it possible to damp the pulsation by change of the capacity of the liquid chamber 61a.
When the discharge pressure of the reciprocal pump is fluctuated, it is necessary to keep the deformation amount of the pulsation suppression diaphragm 62 caused by extension and contraction, within a predetermined range, so that the liquid pressure inside the liquid chamber 61a and an atmospheric pressure inside the gas chamber 61b may balance each other. Therefore, the device as shown in FIG. 4 adopts the following configuration. The device body casing 60 is provided with an automatic gas supply valve mechanism 63 and an automatic gas exhaust valve mechanism 64. When the pulsation suppression diaphragm 62 is extendably deformed by the fluctuation of the liquid pressure inside the liquid chamber 61a, in the direction wherein the capacity of the liquid chamber is increased so as to be above a standard value S, thereby exceeding a predetermined range A, the diaphragm 62 for suppressing pulsation opens the gas supply port 66 via the valve press rod 65 of the automatic gas supply valve mechanism 63, thereby adjusting the gas sealing pressure of the gas chamber 61b so as to be increased. Moreover, when the diaphragm 62 for suppressing pulsation is contractibly deformed in the direction wherein the capacity of the liquid chamber is decreased so as to be below the standard value S, thereby exceeding a predetermined range B, the automatic gas exhaust valve mechanism 64 opens the gas exhaust port 68 by means of a slider 67 abutting against an closed end portion 62a of the diaphragm 62 for suppressing pulsation. As a result, the gas inside the gas chamber 61b is exhausted and adjusted so as to decrease the gas sealing pressure.
On the other hand, a pulsation suppression device for a pump disclosed in Japanese Patent Publication Laying-open No. 8-159016 is shown in FIG. 5A. A switching valve mechanism for switching between gas supply and gas exhaust is shown in FIG. 5B. The proposed device adopts a gas chamber internal pressure adjusting valve mechanism for restricting the change of the capacity of the liquid chamber 61a disposed in the same way as the liquid chamber 61a disclosed in Japanese Patent Publication Laying-open No. 6-17752 so as to be within the predetermined range of the displacement of the capacity. In the mechanism, the switching valve mechanism for switching between gas supply and gas exhaust having an operating rod 69 and a slide valve element 71 is protrusively fitted on an outer side of the device body casing 60. The operating rod 69 is operated according to a displacement of the closed end side 62a of the diaphragm 62 for suppressing pulsation. The slide valve element 71 makes a gas supply and exhaust passage 70 for using both gas supply and gas exhaust, alternatively connect to the gas supply port 66 and the gas exhaust port 68. The gas supply and exhaust passage 70 is operated by the operating rod 69 so as to communicate with the gas chamber 61b. The valve mechanism has the structure as below. The valve mechanism makes the gas supply port 66 connect to the gas supply and exhaust passage 70 when the capacity of the liquid chamber 61a is increased so as to be above the predetermined range. The valve mechanism makes the gas exhaust port 68 connect to the gas supply and exhaust passage 70 when the capacity of the liquid chamber 61a is decreased so as to be below the predetermined range. It has a cylindrical casing 72 provided with the gas supply and exhaust passage 70 which communicates with the gas supply port 66, the gas exhaust part 68, and the gas chamber 61b, and the slide valve element 71 which is coaxially coupled to the operating rod 69 so as to be slidably and displaceably engaged with the inside of the cylinder 73 housed inside the cylindrical casing 72.
Among the two prior arts mentioned above, the device disclosed in the former one, i.e., Japanese Patent Publication Laying-open No. 6-17752, has a structure wherein the automatic gas supply valve mechanism 63 and the automatic gas exhaust valve mechanism 64 are integrally formed with the lower side member 60a as an element of the device body casing 60. Therefore, when either of valve mechanisms 63, 64 is damaged or destroyed, it is necessary to disassemble and repair the device body or replace a whole of the body. This requires much labor, thereby resulting in disadvantage in maintenance and cost. Moreover, the gas exhaust port 68 of the automatic gas exhaust valve mechanism 64 is structurally confined by a phenomenon wherein a gas exhaust valve element 75 drops owing to its weight. Therefore, the closing action is unstable, and the device must be installed so as to keep vertical arrangement relationship between the gas exhaust valve element 75 and the gas exhaust port 68. For example, it cannot be allowed that the device is installed so that the gas exhaust valve element 75 may be horizontally arranged. As a result, kinds of the device are restricted.
The switching valve mechanism for switching between gas supply and gas exhaust disclosed in Japanese Patent Publication Laying-open No. 8-159016, i.e., the latter one, adopts a configuration wherein one valve is used for both the gas supply and the gas exhaust. Therefore, it is not necessary to disassemble the device body. It is efficient only to disassemble the switching valve mechanism and repair or replace it. In case of closing the gas supply port 66 and the gas exhaust port 68, this does not structurally rely on the weight of the gas exhaust valve element 75, which is different from the former one, thereby making it possible to overcome the problem in the former one. However, on the other hand, it has disadvantages as below. The structure of the switching valve is very complicated, the seal of the slide valve element 71 is so difficult, and it protrudes to the outside of the device body casing 60, whereby a whole of the device is bulky and large-sized.
The present invention has been conducted in view of the above mentioned circumstances. Especially, an object of the present invention is to provide a pulsation damping device for a pump, which can be installed in either vertical or horizontal style by improving the gas exhaust valve mechanism. This can diversify kinds of the device.
Moreover, another object of the present invention is to provide the pulsation damping device for a pump whose structure is simple, which can be economically produced, and wherein it is easy to maintain the gas supply and exhaust valves.